1. Field of the Invention
The present invention relates to voice processing method and voice processing device suitable for real time voice communication system.
2. Prior Art
Real time voice communication such as telephone is usually carried out by connecting users' terminals with line and transmitting voice signal on the line. However, today with well-developed network such as the Internet, study of real time voice packet communication such as Internet telephone, in which voice signals are encoded and voice packets with the encoded signal on their payload parts are transmitted, is widely being done.
As a method for real time voice packet communication, following method is known. Namely, by a device at a transmitting side, voice signal is compressed using a certain method such as A-law or μ-law, then sampled, and PCM (pulse code modulation) voice sampling data is generated. The PCM voice sampling data is then placed on the payload part of the voice packet, and transmitted to a device at a receiving side via network. However, when this method is used, if voice packet is lost by network congestion, or if bit error occurs in voice packet during propagation, the device at the receiving side cannot reproduce voice for that faulty voice packet. This can result in degradation of voice quality.
Also, so far, a decoder and an error detection device do not send to the following encoder information that there is loss of packet or bit error in packet. Therefore, the encoder encodes these defective packets without taking any measures against defection. This results in degradation in voice quality.